Angular Normalization of ENVISAT ASAR Data over Sahelian-grassland Using a Coherent Scattering Model

ENVISAT-ASAR acquires data at different incidence angles. For temporal soil and vegetation parameters retrieval it is necessary to normalize the radar data for the angular behavior of the radar backscatter. A simple method for characterizing the angular behavior is by plotting the measurements of the backscattering coefficient during the dry season (stationary target) as a function of the incidence angle and considering that this angular dependence is conserved throughout the rainy season as well. However, this method is not sufficiently precise for data gathered in the rainy season since the scattering mechanisms of the vegetation and soil are different. Instead, we propose the use of a coherent scattering model for vegetation in order to carry out a more precise angular normalization. With this method, a higher precision is obtained for the normalization of the backscattering coefficient at VV polarization during the rainy season, in whichthe main contribution to the backscatter is attributed to vegetation.